Tandem allotting system



May 29, 1923.

AQE. LUNDELL TANDEM ALLOTTING SYSTEM /M Ven/0f v Awe/4f wia/@l ffy.

May 29, 1923.

A. E. LUNDELL TANDEM ALLOTTING SYSTEM Flltd May 2l 1919 2 Sheets-Sheetf3 m59@ Sn Ltoz Inu( l. DE o w Sum,

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vnarran stares ears-ttt @..LFFHCEG ALBEN E. LUNDJELL, 0F NEW YORK, NPY.,ASSIGNOR T0 WESTERN ELECTRIC COMPANY, ENCUEPOEATEDOF NEW YORK, Y., ACDRPOBATION 0F NEW YORK.

. msnm enterarme 'srs'.rnra.

To all whom t may concern;

Be it known that 5I, ALBEN E. LUNDELL, a citizen v-of the United States,residing at New York, in the countyof Bronx and State of New York, haveinvented certain'new and useful Improvements in Tandem AllottingSystems, of which the following is a full, clear, concise, and exactdescription.

This invention relates to automatic telephone 'exchange systems and morepartlcularly to the distribution of apparatus in such systems.

In telephone systems employing the inder 1switches it has been customaryto provide an allctting switch for each roup of line iinders, thefunction of this al otting switch being to repare a finder switch foroperation, anclp as soon as such allotted finder switch is taken for useto hunt out another idle finder switch and prepare .it for operation. Adefect of this arrangement is due to the fact that the group of'finderscontrolled by an allotter is necessarily small, since, if a large numberof switches are controlled by a single allotter, considerable time imight'be needed before the allotter could pick out an idle one incasemany of the intervening switches were busy. uring this time intervalit might be possible that several calls would be originated.

If, now, it is desired to utilize a 500 point switch as a line finder,and distribution is to be on a 10% basis, 50 line finders would have tobe provided to serve this group. The allotter would then have to huntover a possible contacts and might frequently have to pass over laconsiderable number before finding an idle one. The time required forthis would be, as pointed out above, an undesirable feature.

It is the object of this invention to provide an arrangement in which alarge number of finder switches are commonly available to thesubscribers of a group and in which there is'never more than one finderin a position tovbe started at" any given time. The object of theinvention has been set forth in connection with linelinder switches andthe following specification will explain the operation of a system.embodying this type .of switch, but it is obvious that the principleinvolved is capable of adaptation to la large variety of switches whosefunctions may be of various characters. The ineppncmon mee may a1, una.vserial no. aeaseo. i

vention is, therefore, not to be restricted except as to the subjectmatter set forth in the claims.

Acfeature of the invention is the sionJ of' a tandem arrangement of a'lotter switches, there being `a central, or master allotter switch, asit will be termed hereinafter, which is individual to a main group ofline nders. ln addition to this master allotter switch therel will be anallotter switch individual to each smaller group of nders into which themain group is divided. The arrangement is such that the allotting ofanygivenvinder is the result ofthe joint operation of the masterallotter and the allotter individual to some one of the smaller groups.

An additional feature of the invention is an arrangement by which theallotters of the rovismaller groups pre-select an idle finder, so A thatas soon as the master allotter moves into connectlongwith this sub-groupallotter, the se uence syvitch associated with the finder wi beadvanced.

A further featureof the invention resides in the provision of meanswhereby the master allotterwill'notstop when it comes into operativerelation with a group allotter in whose group there are no idle finders.

A. still further feature of the invention is provlded by an arrangementsuch that the master allotter moves from sub-group to sub-group aftereach allotting operation thus'producmg a system in which every" finderhas an equal chance of being brought into use. This proves a decidedadvantage over ay system in which certain of the devices are broughtinto use repeatedly while others do relativelylittle work.I i

It is-thought that the inventionk will best be understood from'thefollowing detailed description, reference lbeing had to the accompanyingdrawings. v

ln the drawings, Fig. 1 .diagrammatically indicates a ymain group offinders, the first finder of the first group being provided withoperating circuits, while the other finders have only certain portionsof their operating circuits shown. i

vF ig. 2 shows a master allotter individual to the main group, and oupallotters individual to the varlous smjler groups insuch eat group. InFig. 2 he masterallotter 1s shown at the left-liand portion of theydrawing, while the group allotters are provided with designations whichwill readily identify them. g

If we assume that the switch is of .500line capacity u line finderswhich will serve this group. These 50 line finders will constitute whatp has been termed a great grou The great moves out of position 1 andinto group is divided into five sma er groups of 10 line finders each,each one having an allotter associated with it.

The line finder switch shown in Fig. 1 is of the power driven type.vr Inpractice this switch would be of the multiple brush type havin r fivenormally inoperative brush sets, one o which is rendered operative asaresult of a brush selecting operation. Since, however, the invention isnot concerned withany particular ty e of switch, it has been assumedthat the ine finder shown is provided -with only one brush set which isarranged to be advanced in a continuous mo.

tion over the entire group-of 500 terminals.

IThe mechanical constructlon of such a switch will be entirely obviousto one skilled in the art when considered in connection with the circuitto be described. In order to prevent the disclosure from becomingunnecessarily complicated, it has vbeen assumed that the line finder isdirectly connected to a connector switch which will make connection to acalled subscriber. Thisl switch lhas been shown vas being a step-by-stepswitch, and may be of anyone .of several well-known types of two motionstep-by-step automatic switches. A switch of this ty e is shown inPatent No. 1,252,420'to O. F. 1 orsberg. The allotter switches are allof similar construction and may referably be of a mechanicalf structuresimi ar to that shown in Patent No. 1,127,808, issued to E. B. Craft andJ. N. Reynolds. The invention is, however, obviously not limited to theemployment of an alotting switch of this type.

The operation of the system is as follows: When the subscriber atsubstation 1 removes his receiver from the switchhook, a circuitviscompleted from grounded battery, left-hand winding' of line relay 2,outer amature and back contactl of cutofil rela 3, over the loop of thecallin subscribers ine, inner armature and bac contact of rela 3right-hand winding of relay 2 to groun :A ine relay 2 energizes and`completes a circuit from grounded battery, power magnet of 'se uenceswitch 4, which, it must be understoo ,'was rplaced into position 1 inreadiness for ioperation, upper contact of sequence switch ,spring 5,left-hand armature and front con- /tact of relay 2 to ground. Sequenceswitch 4 under the control of its master contact 6j position 2. Inposition 2 of sequence switc 4, a cir-l cuit is completed from groundedbattery, winding of up-drive magnet 7, armature and we may then assumethat there are `ergized in this circuit, rela back contact of test relay8,,contact of ses quence switch `spring 9 to ground. The finder brushes10, 11, 12 are moved upwardl over the terminal bank in search of the cal1r`1lg line under the control of magnet 7. l hen the test brush 10engages the test contact of the calling line, a circuit is completedfrom grounded battery, right-hand armature and front contact of relay 2,resistance 14,test brush 10 and its associated contact, lower contact ofsequence switch spring 13, winding of relay 8 to ground. Irlparal e1 acircuit is com leted from grounded battery', winding o cut-'off relay .3to ground as described. Relays 3 and 8 are en- 8 at its armatureopening' the driving circuit of magnet 7, thus bringing the brush set torest upon the desired terminal. Cut-ofi` rela 3 upon energizaton removesthe control o the calling subscribers line relay in the well-knownmanner, and provides a holding circuit for relay 8. Relay 8 is marginaland will not operate while test brush 10 is passing over the terminalsof non-calling or busy lines. If these' lines are busy as callingQlines, a shunting `ground, is provided by way of re'- sistance 15 ofthe finder associated with .such other line to prevent the operation ofcalling, the resistance of cut-off relay3 is sufficient to' prevent theoperation of line' 10o' relay 8, it being necessary-that battery hesupplied both through the winding of relay 3 and through resistance '14in parallel in orderthat relay 8 ma, be energized. The current flowingthroug relay"3 is not lsufii- 105 cient to cause the actuation of relay8, but is sufficient to maintain this relay energized after it has beenactuated. v

The energization of relay 8 also completes y a circuit from groundedbattery, power magnet of sequence switch 4, armature and front contactof relay 8, contact of sequence switch spring 9 to ground, for movingthis se-l quence switch out of position 2 and into po- 1 sition 3.Whenseuence switch 4 reaches4 115vv position 2%, a groun ed shunt pathis placed` on the test terminal of the calling line to prevent, itsseizure by other hunting line finders. In position 3 of sequenceswitch4, the subscribers line is connected to thestepbylstep connectorby way of sequence switch springs 17 and 18.`

A circuit' is now completed from grounded battery, left-hand winding ofline relay 19. over the upperv side ofthe line to the callingsubstation, thence by way of the4 lower side of the line and right-handwind-l ing of relay 19 `to ground. -Relay 19 is' energized andcomdpletes a circuit from ground-v ed battery, win ing of slow-releaserelay 20,

f y menacer armature and front contact of relay 19 to ground. Relay 20is energized in vthis l, circuit.

The calling subscriber now operates his impulse sending mechanism 21 tosend the rst digit of the calling subscribers num# ber; Since the finderis directly connected to a 100'point connector switch, it will only benecessary for him to dial the tens and units digits. In response totheoperation of the dial, the line circuit is intermittently interrupted,causing in turn the intermittent operation of relay 19. yUpon the firstdeenergization of relay 19, a circuit is comtion of the armature ofrelay 19, a circuit is group step.

completed from grounded battery, winding of primary stepping magnet 24,lower contact. of sequence switch spring 25, armature and front Contactof relay 20, armature and back contact of relay 19 to ground. YUpon eachenergization of magnet 24, the brushl shaft of .the connectorswitch isadvanced a Upon the termination of this series of impulses, relay 19remains energized for a relatively lon period, causing thedeenergization of re ay 22. Relay 22 upon deenergization completes acircuit from grounded battery, power magnet of sequence switch 4,

' upper-contact of sequence switch spring 23,

armature and back contact 'of relay 22 to ground for moving thissequence switch out of position 4 and into position 5.

The subscriber now sends the units series of impulses; As before, thefirst deenrgization-of relay 19 causes the energization of relay 22.Relay 22 attracts its armature and advances. the sequence switch intoposition 6 over a circuit identical with that for moving sequence switch4 from position 3 to position 4. Each retraction of the armature ofrelay 19 also completes a circuit from' grounded battery, winding ofsecondary stepping magnet 26, upper contact of sequence switch spring25, armature and front contact of relay 20, armature and back contact ofrelay 19 to ground. Upon each energization of magnet 26 the'brushes 2728 and 29 are advanced over a set of terminals in the selected group.Upon the completionotl the sending of the second series of impulses,relay 19 remains energized,

' causing the deenergization of relay 22, which completes a circuitremoving sequence switch 4 out ofposition 6 and into position 7. i

Assuming that the called subscribers line is idle, ar circuit iscompleted as soon as sequence switch 4 reaches position 7 extending fromgrounded battery, power magnet of sequence switch 4, lower contact ofsequence switch spring 36, left-hand armature and back Contact of relay33,`tovground, for moving the sequence switch'out of position 7 andintro position 8.

In pos1tion 8 guarding potential is applied to the test terminal of thecalled line by way of sequence switch spring 37 and resistance 16. AtVthe same time ringing current is supplied to the called sub-stationfrom a source of alternating current, winding of relay 38, contact of.sequence switch spring 39, brush 27, over the upper side ofthe calledline, through the sub-station apparatus, including the bells andcondenser, over the lower side of the line, brush 28, contact ofsequence spring 40, to ground. When the called subscriber removes ,hisreceiver, the

current flow through relay 38 is increased sufficiently to allow thisrelay to attract its armature, thus completing a circuit from groundedbattery, power magnet of sequence switch 4, upper right-hand contact ofsequence switch spring 41, armature and front contact of relay 38, toground, for moving this sequence switch out of position 8 and intoposition 9.

Position 9 is the talking position and the calling line is connected tothe called line by way of sequence switch springs 30 and 31.v Duringconversation, battery is supplied'to 'thecalled line through thewindings of a resistance 32. After conversation is completed the callingsubscriber replaces `his receiver on'the switchhook, causing thedeenergization of relay19 which, in turn, causes the'release of relay20. A circuit is now completed from grounded battery, power -magnet ofsequence switch 4, lower contact of sequence switch spring 41, armaturesand back contacts of relays 20 and 19, to ground, for moving thesequence switch out of position 9 and into position 10.

In position 10 a circuit is completed from grounded battery, winding ofdown-drive magnet 42,. contact of sequence lswitch spring 43, `toground. Under the control of magnet 42 the finder brush set is returnedto its normal iposition.` When the commutator brush 44.v p mounted onthe `brush carriage, engages the `normal commutator segment 45, whichoccurs when the switch is fully'restored, a circuit -is completed fromgrounded` battery, power magnet of sequence switch 4,

upper left-hand contact of sequence switch spring 41, segment 45, brush44, to ground, for moving the sequence switch out of posilower contact,whereupon a,- circlt is com- A pleted from grounded battery, winding of.power magnetof sequence switch 4, lower left-hand Contact of sequenceswitch spring 23, lower contact of off-normalspring 47, contact ofsequence switch springI 48,to ground, for moving the sequence-switch 4out of Vposition 11 and into position 18. The sequence switch remains inposition 18 until the finder is reallotted for service.

Assuming now that at the time the lbrushes 27, 28 and 29 were placed onthe terby way of sequence switch spring 37 and' resistance 16 of theconnector whichv has previously seized such line, provided that the lineis busy as a called line. v'as acalling line, the Aground for energizingrelay 33 will be supplied from the test brush -1 by way of the uppercontact of sequence switch spring 13 and resistance 15 associline, Relay33 upon energization locks up through its inner right-hand armatureuntil sequence switch 4 leaves position 9. As soon as relay. 33 isenergized, a circuit is completed for supplying busy tone to the callingsubscribers line. This circuit extends from ground through the secondarywinding of an induction coil, the primary circuit of which includes aninterrupting device and battery, through the outer right-hand armatureof relay 33 and thenceover the lower talking conductor, through thecalling sub-station apparatus, over the upper side of the line andthrough the left-hand winding of relay 19, to grounded battery. Thistone will inform thecalling subscriber that,the desired line is busy.l l

Relay 33, at its' left-hand armature, co pletes a circuit from groundedbattery, power magnet of sequence switch 4, upper v,right contact ofsequence switch spring 36, left-hand armature and front contact of rclay33, to ground, for moving) this sequence switch through positions 7, 8and 9 and into d) i *I y ,y e incassa position v10, whereupon thedown-drive niagated with the finder which has selzed the finders will beinf some net becomes efective vand the release of the finder andconnector take place aspreviously described. l i The operation ftheallotting system will now be described. Itwas assumed that at the timethe calling subscriber at sub-station l'initiated a call, thesequence'switch'of the first finder was in ositionl. t this time theallotter of the u rst group will also be` in position 1/and the masterallotter will' be in .position 1. 1

After the finder istakenfor use and its associated sequence switch movesout of position 1,ta circuit will ,be completed for advancing the masterallotter when sequence switch y4 reaches position 1%. This circuitconductor 102,5lower contact `o sequence switch. spring 50, to ground.The master allotteru moves from positionq 1 to po'. sition 2 under thecontrol of its normal controlling spring 103. The master allotter willcome to rest in position 2 provided that there is an idle finder in thesecond group;

It all the finders `in the -second Lgroup are busy, a circuit will becompleted from`` Iground battery, power magnet of master allotter 100,the upper right-han contactV of allotter'spring 101, conductor 104,through the contacts7105, 106, 107, 108, etc., of the finders of thesecond group, to ground. In response to the completion of this circuitthe master allotter moves on to position 3, at which time it will extendthe control 'circuit to contacts controlled by the allotter individualto the third group. c Y

When the finder whose operation has just been describe-.1, reachesposition 2, a circuit is completed frpm grounded battery, power magnetof allotter 200, which is individual to the first group of finders,upperleft-hand contact of allotter spring 201, conductor 202, contact ofsequence switch spring 51, to

ground, for movingthis allotter out ofposition 1 in search 61:' anotheridle finder. The allotter 200 will rotate until a' Iinde'r whosesequence switch is standing in position 18, is found, due to the factthat the circuit Aof the upper magnet of allotter 200 is com leted byway of a sequence switch springslmilar to sequence swltch spring 51 onallbusy finders, since'the sequence switches of busy u Jpositionincluded in the positions 2 to 17.

As soon as allotter 200 finds a finder whose sequence switch is inposition 18, the allotter comes to rest and the controlfcircuit b way ofconductor 203 is extended to' such nder. The allotter v200 cannot,however, move this sequence switch to a position wherein the finder maybe! started, since the control cir-` iso rasato? cuit by way ofconductor 203 is not completed until the master allotter arrives inposition 1.

All ofthe group allotters operate as has just been described forallotter 200, that is, they prcselect or preallot a finder which is inposition to be started and, as soon as the control circuit is extendedto them in response to the operation of the master allotter, the controlcircuit becomes effective to advance such preallotted nder into positionto be started. l

For instance, when the first finder of the first grou is inreadiness-tor.reallotment, that is, wlien its sequence switch is inposition 18, allotter 200 may preallot this iinder by stopping inposition 1.

The finder sequence switch will not be advanced, however, until masterallotter 100 reaches position 1, at which time a circuit will becompleted from grounded battery, power magnet of sequence switch et,lower contact ot' sequence switch spring 5, conductor 70, upperleft-hand .contact of sequence switch spring 204:, conductor 203, upperleft-hand contact of master allotter spring 109 to ground, for movingsequence switch i out of position 18 and into position 1.

From the fore oing it will appear that the following desirale resultsare obtained from a system of this character, due to the fact that eachone ot the five group allotters is a preallotting switch. Any time thatthere is an available finder switch it can be moved into position to bestarted as the result of a maximum movement of ive steps of the masterallotting switch, since if all the finders in the tour groups are busy,they will be passed over one by one, as a result of a single step ot themaster allotter and then the preallotted finder in the fifth group willhe seized. ln this way a large number of finders may be allotted in anextremely short space of time.

What is claimed is:

l. ln an automatic telephone exchange system, a main group of automaticswitches, said main group of automatic switches being divided intovsub-groups, an allotter switch individual to said main group ofautomatic switches, an allotter switch individual to each of saidsub-groups, means to determine which of said switches shall be taken foruse as a result of thecooperation of said main,

'said main grou of automatic switches being divided into su -groups, acontrol switch individual to said main group of automatic switches, acontrol switch individual to each of said sub-groups, means to controlcertain operations of said automatic switches as the result of thecooperation of said main group 'control switch and one of said sub-groupmaster control switch, a plurality of automatic switches, a controllingcircuit for operating said automatic switches, means responsive to theoperation of said control switches for preparing a portion of saidcontrolling circuit, means including said master control switch torender said controlling circuit effective andmeans to advance saidmaster control switch each time that a controlling circuit is madeeffective.

4. lin an automatic telephone exchange system, a plurality of groupallottcr switches, a master allotter switch, automatic switchescontrolled hy said allottcr switches and arranged in groups, means tooperate said group allotter switches to pre- 'allot an automatic 'switchin each group when there is a switch in such group in condition forallotment, means under the control of said master allotter to rendersaid pre-allotment eective to put an automatic switch into use. means toadvance said master allotter into cooperative relation with the groupallotter of a new group each time that a switch is taken for use, andmeans to bring said master allotter to rest in cooperative relation witha group allotter only when there is a switch in such group available foruse.,

5. lin an automatic telephone exchange system, a plurality of groupallotter switches, a master allotter switch, automatic switchescontrolled by said allotter switches and arranged in groups, lmeans to ocrate said group allotter switches to preal ot an automatic switch ineach group, means under the control of said master allotter to rendersaid preallotment eective to put an automatic switch into use, and meansto advance said master allotter into coo erative relation with the groupallotter o a new group each time that a switch is taken for use.

6. lin an automatic telephone exchange system, a main group of automaticswitches, said main group of automatic switches being divided intosuboups, a control switch individual to said main group of automaticswitches, a control switch individual to each sub-group of automaticswitches, means to control certain operations ot said automatic switchesas the result of the co-operation of said main group 'iid system, aplurality of control switches, a

conti'ol switch and one of said sub-group control switches, and means toadvance said main group control switch into cooperative relation withthe control switch of a new sub-group each time that an. automaticswitch reaches a cert-ain stage of operation. 7. Inf' an automatictelephone exchange system, a main group of automatic switches, said maingroup of automatlc switches being divided into sub-groups, a controlswitch individual to said main group of automatic switches, a controlswitch individual to each sub-group of automatic switches, means tocontrol certain operations of said automat-ic switches as the 'result ofthe cooperation of said main group control switch and one of saidsub-group control switches, means to bring about such cooperation onlywhen there is at least one automatic switch in a sub-group in a certaincondition, and means to advance said main oroup control switch each timethat a contro of one oisaid automatic switches has been e'ected.

8. ln an automatic telephone exchange system, a plurality of controlswitches, la master control switch, automatic switches controlled bysaid control switches, controlling circuits for operating' saidautomatic switches, means under the control of said control switches forpreparing portions of said controllin circuits, means under the controlof sai 'master control switch to render said controlling circuitssuccessively effective, and meanssto advance said master control switcheach time that a controlling circuit is made eilective.

9. In an automatic telephone exchange system, a group of multipleterminals, a group of automatic switches having common access to saidmultiple terminals, said group of automatic switches being arranged insub-groups, means to allow one only of said group of automatic switchesto be in position to be started at a given time, a control switchindividual to said main group of switches, a control switch individualto each sub-group of switches, means under the control of said maingroup control switch and said sub-group control switches to determinethe order in which saidswitches are moved into a position to be started,andv means to advance said main group control switch each time that oneof said automatic switches is stanted.

ln witness whereof, l hereunto subscribe my name this 19th day of May,A. D. 1919.

ALBEN lil. LUNDELL.

